Shock wave reactions

ABSTRACT

It has been found that the efficiency of shock wave reactions can be greatly improved by using mercury vapor as a diluent in the reaction gas. By using reduced pressure in the reaction gas Hg mixture the boiling point of the Hg is reduced and after the reaction the Hg is easily separated merely by allowing the product gas to come to atmospheric pressure whereupon the Hg condenses out. Even at pressures of atmospheric or greater the Hg is easily separated from the product gas because of its high boiling point.

Unlled b13168 Fawn! [111 3,739,063 Lauer June 12, 1973 [5 SHOCK WAVEREACTIONS 2,902,337 9/1959 Glick et al. 23/1 R 3,251,648 5 1966 A1 (1 t1 23 1 R X [75] James Laue" Wynne 3,300,283 1i1967 23/284 [73] Assignee:Sun Research and Development Co., 33307317 3/1967 23/1 R x PhiladelphiaPa. 3,406,014 10/1968 Guernen 23/221 [22] Filed: 1970 PrimaryExaminer-Edward Stern [21] Appl. No.: 102,521 Attorney-George L. Church,Donald R. Johnson,

Related U.S. Application Data John McNany at [63] Continuation-impart ofSer. No. 795,926, Feb. 3, [57] ABSTRACT 1969, abandoned.

It has been found that the efficiency of shock wave re- 52 us. Cl.423/648, 423/579, 423/659, acfims can be greatly impmved by Sing mercury423/415 423/443 260/679 vapor as a diluent in the reaction gas. By usingreduced 51 Int. Cl. c011; 1/03 cdlb 13/02 Pmsure gas Hg mixture theboiling [58] Field of Search n 23 R B 210 R point of the Hg is reducedand after the reaction the l-lg 23/212 R 221 202 423/579 6 is easilyseparated merely by allowing the product gas to come to atmosphericpressure whereupon the Hg condenses out. Even at pressures ofatmospheric or [56] References Cited greater the Hg is easily separatedfrom the product gas because of its high boiling point.

3 Claims, 11 Drawing Figures PATENTEU 2 3. 739 O63 SHEET 1 of 2 /)ZBUTANE AND H VAPOR WAVE ENGINE /0 ipx /d SEPARATION HYDROGEN ZONE Z6 75ACETYLENE ETHYLENE AND OTHER PRODUCTS FIG 2. FIGS.

fl Q 55 b REACTA N 56 omyg f 37 J0 GAS w 4/ t Z6 PRODUCTS 42 16 BYJAMES27 LAEER ATTY.

PAIENIED m1 219?;

sum 2 or 2 FIG. 6.

REACTANTS DRIVING ,GAS

PRODUCTS FIG! I.

REACTANTS M G W N R D Omvm A PRODUCTS mvewoa: BY JAM [:5 L. LAUER ATTY.

SHOCK WAVE REACTIONS CROSS REFERENCE TO RELATED APPLICATION Thisapplication is a continuation-in-part of application Ser. No. 795,926filed Feb. 3, 1969, now abandoned.

The present invention relates to an improvement in endothermic chemicalreactions carried out by subjecting a reactant material to one or moremechanical shock waves, thereby to produce a high temperature in suchmaterial for a very short period of time. More particularly theinvention relates to the use of mercury vapor as a diluent in thereaction gas.

In various chemical reactions, it is necessary that very hightemperatures be employed and that the residence time of the reactants atthe elevated temperature be very short. Nitrogen fixation is welladapted to this type of reaction. It can, for example, be used for themanufacture of nitric oxide from its elements in accordance with thereaction:

or from C0, in accordance with the equation:

N,+2CO, 2NO+2CO as well as for the production of acetylene and hydrogencyanide from a hydrocarbon as exemplified by the following chemicalequations:

2Cl-l CJ-l, 3H:

and

ZCH, N, ZHCN 3H,

For these equations, which may in effect be thought of as a singlereaction, to proceed, it is necessary that very rapid heating of thereactants from a temperature not greater than 500C. to a temperature notless than 1,760C. be accomplished. The maintenance of the reactants toolong at temperatures in the range of 500 to 1,760C. results in excessivereaction, producing undesired products such as carbon.

It is therefore necessary that the heating through this crucial range beextremely rapid. It is also necessary that upon reaching the reactiontemperature, which is for example in the range of l,760 to 2,250C., thereactants be maintained at such temperature for only a short time. It isfurther necessary that the reaction products be rapidly cooled from thereaction temperature to a temperature not substantially greater than880C.

Shock wave procedures have been found to be particularly advantageous inthe type of reaction described above. This is accomplished by subjectingthe reactants to one or more mechanical shock waves thereby to produce ahigh temperature and pressure in the reactant material for a very shortperiod of time. In fact the distinguishing characteristic of shock wavereactions is the large and discontinuous rise in temperature andpressure caused when the shock wave passes through the reaction mixture.

Other reactions that are of the type suitable for shock wave processinginclude such reactions as the cracking of butane to ethylene, thermaldissociation of water vapor to hydrogen and oxygen (providing hydrogenfrom an abundant raw material), dissociation of carbon dioxide intocarbon monoxide, the formation of acetylene from methane, ethane orethylene, the formation of carbon disulfide from carbonaceous,hydrogenous and sulfur containing material, the formation of methanoland formaldehyde from methane and oxygen and many others.

The required heating and cooling may be conveniently effected in a shocktube. A shock tube is a pipe in which a gas or a gas mixture (termed theprocess gas) can be heated very rapidly to very high temperature byanother gas, the driving gas, non-isentropic compression being theheating mechanism. That is to say, the process involves compression ofthe process gas by another gas, the driving gas, which latter works in away similar to a mechanical piston. The compression is the result of ashock wave produced in the tube.

The heating is followed almost immediately by rapid cooling throughexpansion. If there is a frequency of equivalent independent shock tubeprocesses, the result is essentially a continuous flow process.

The gas or mixture of gases which is acted upon in the shock tube may betermed the reagents, a process gas, a reactant mixture, a charge gas, areactant material, or a process mixture.

It is in many cases advantageous to add an inert gas to the reactiongas, so as to increase the value of ratio k of the mixture to be reactedand subsequently, to ob tain a higher temperature in the reactor at agiven pressure. The constant k as used herein is the ratio of Cp (thespecific heat of the gas at constant pressure) to Cv (the specific heatof the gas at constant volume). Thus in order to obtain the mostfavorable temperature/pressure relationship it is often desirable to mixthe gas or gas mixture which is to react, with an auxiliary carrier gashaving a higher k value than the first mentioned gas or gas mixture.This use of a carrier gas with a suitable k value is particularlyimportant when hydrocarbons are to be reacted, e.g., cracked, in view ofthe low k values of hydrocarbons and particularly of the heavierhydrocarbons. In the past it has been the practice to employ a gas suchas steam, nitrogen, helium, neon, or argon as the carrier. Preferablythe carrier gas has been inert in the reaction but not necessarily so.For example in a reaction using a magnetically driven shock wave toproduce acetylene from methane (k 1.30) the reaction gas is diluted withnitrogen (k 1.40) which is reactive to produce hydrogen cyanide, but byadjusting the mole ratios of methane and nitrogen better yields ofacetylene can be obtained than in the absence of a diluent as shown inTable I.

TABLE 1 Run No 1 2 3 4 5 6 Original Pressure in 22.4 23.0 22.3 24.4 23.123 Reactor (mm. Hg) Energy input (Watt-hrs.) 1.07 1.96 1.83 1.76 1.611.74 M01 percent N, in charge 79.9 65.7 55.2 58.2 37.2 0 Mol percent CHin charge 20.1 34.3 44841.8 62.8 Yield (M01 percent) based on CH. incharge:

Acetylene 31.2 54.6 61.2 54.9 47.4 0

In addition to a particular diluent gas having a favorable k a highmolecular weight gas is preferable since the strength of the shock waveis a function among other things of the molecular weight of the reactantgas. An extensive discussion of the theory and application of shockwaves in this regard can be found in Shock Waves in Chemistry andPhysics, John N. Bradley, 1962, Great Britain, Bulter & Lanner, Ltd.,particularly Chapters II and III, pages 13-109.

Of the carrier gases previously employed argon is usually used asdiluent in shock tubes because it is inert, has the highest possible k(1.67) and has a reasonably high molecular weight, i.e., 40.Unfortunately argon is expensive and would make the economics of acontinuous shock wave process unattractive. Furthermore, argon is noteasily separated from the products of shock wave reactions.

The present invention provides a novel diluent that has a high kconstant, high molecular weight, and is easily separated from othermaterials. Briefly the present invention is an improvement in theprocess of subjecting a gaseous reactant material to one or moremechanical shock waves wherein the improvement comprises adding amercury vapor diluent into said gaseous reactant. Mercury vapor has a kof 1.67, a molecular weight of 200.59 which is over five times that ofargon, and is separable from other gases by condensation.

The obvious disadvantage of mercury vapor is of course the boiling pointof mercury (357C). This problem is readily overcome when the practicaloperation of any shock wave process is considered. In actual operationpreheating of reactant gases is employed for the achievement of adequatereaction temperature for high yields. For example, in my [1.8. Pat. No.3,231,482, it is stated that in the preparation of carbon disulfide frommethane and H the reactant gases should be preheated to 125 to 425C.Usually it has been the preferred procedure to introduce the reactantsat one atmosphere or lower pressure; lower pressures are advantageous inthat they facilitate the provision of a high ratio of driving gaspressure to reactant gas pressure, and such ratios favor the obtainingof high temperatures as a result of the shock wave. Other initialtemperatures and pressures can be employed if desired, although initialtemperatures above 425C. should be avoided in order not to obtainpremature and excessive reaction especially with organic compounds priorto subjection to the shock wave. With more thermodynamically stablecompounds, for example, water, higher temperature may be tolerated. Theuse of lower pressures will reduce the boiling point of mercury andsignificantly simplify the separation of Hg vapor from the productgases. This is achieved merely by allowing the pressure of the productgases to come to atmospheric, since the shock wave technique (discussedbelow in more detail) can result in the temperature of the product gasesbeing of the same order of magnitude as the reactant gases, thetemperature of the Hg vapor will be below its boiling point atatmospheric pressure and will immediately condense. In any event the Hgis easily separated from the other product gases merely by cooling thegases to below mercurys boiling point corresponding to its partialpressures, at this temperature most other components of the product gaswill still be vaporous.

The mercury vapor is added to the reactant gases prior to feeding themto the reaction zone at a volume ratio of reaction gas to Hg vapor inthe range of 1:2 to lz200.

Prior to the first shock wave, the reactant gases, including the Hgvapor are held preferably at a temperature in the range of 125 to 425C.and at a pressure in the range of from 0.1 to 10.0 atmospheric, thetemperature and pressure being adjusted to provide conditions underwhich the mercury is in a vaporous state.

The invention will be further described with referv ence to the attacheddrawings wherein FIG. 1 is a schematic flow diagram of a process systemfor the preparation of ethylene from butane, the system including a waveengine for producing the mechanical shock wave.

FIG. 2 is a sectional elevation of the wave engine,

FIG. 3 is a sectional left-hand end view on the line 3-3 of FIG. 2,

FIG. 4 is a left-hand view of FIG. 2,

FIG. 5 is a sectional right-hand view on the line 5-5 of FIG. 2,

FIG. 6 is a development of the cylindrical wave engine of FIG. 2 andillustrates the paths of gas flow through the wave engine, and

FIGS. 7 to 11 are views of a second embodiment of the wave engine, theviews corresponding to those of FIGS. 2 to 6, respectively, except thatFIG. 9 is an isometric drawing, whereas the corresponding FIG. 4 is not.

Referring to FIG. 1, butane and Hg vapor are introduced through line 12into wave engine 10. Hydrogen at elevated pressure is introduced throughline 14 into wave engine 10 and subjects the previously introducedbutane and Hg vapor to a shock wave in a manner which is subsequentlydescribed more fully. The butane is thereby heated to reactiontemperature and cracks to form ethylene with acetylene as by-product.The reaction products, together with unreacted butane and Hg vapor, areremoved from the wave engine through the line 18. Hydrogen is removedseparately from the wave engine through the line 20.

The reaction products and unreacted material are introduced into aseparation zone 22 wherein a plurality of operations are carried out toobtain the respective constituents in purified form. Hydrogen, which wasformed in the reaction is separated by known means such as diffusionthrough a palladium tube and is removed through a line labeledHydrogen". A portion of this hydrogen is introduced into compressor 16for subsequent use in another cycle of the wave engine operation. Theremainder of the product hydrogen is withdrawn as a product of theprocess.

Ethylene is separated from the remaining gases by cooling. All gasesmay, of course, be separated by diffusion or other standard procedures.Acetylene is subsequently separated from the remaining gases byabsorption in a copper salt solution or by other known means forrecovering acetylene from gaseous mixtures. The remaining butane isrecycled to the wave engine through line 30.

Mercury is separated by condensing and is passed through 31 to avaporizer (not shown) for reuse. In the operation illustrated in FIG. 1,the hydrogen acts as a driving gas to cause a shock wave in the reactantmaterial. This hydrogen is substantially unchanged as a result ofpassage through the wave engine, and is recycled through line 20 and thecompressor 16. If the hydrogen withdrawn through line 20 containssubstantial quantities of other gases in the system, it can be passedthrough the separating system 22 prior to recycle to the wave engine 10,though this is usually not necessary.

The wave reactors used in the process of this invention are well knownin the art, for example wave reactors of the types shown and describedin U.S. Pat. Nos. 2,832,666; 2,902,337; 3,254,960; 3,262,757 and3,272,598.

Referring to FIGS. 2 to 6, the wave engine is illustrated therein inmore detail. The wave engine comprises a cylindrical rotor 32 to whichare attached a plurality of longitudinal vanes 34. These vanes provide aseries of channels or tubes 36 having open ends. The tubes are boundedinwardly by the rotor 32, outwardly by the stationary cylindrical shell37 of the wave engine, and laterally by the vanes 34. The rotor andattached vanes are rotated by means of a motor not shown, and a shaft39. The shaft 41 is seated in a bearing not shown.

The wave engine is closed at the ends by stationary end plates 38 and40. Positioned outwardly from the end plates and adjacent to the ends ofthe tubes 36 are two stationary manifolds at each end of the waveengine. The manifolds 50 and 52 are positioned at the left-hand end, andthe manifolds 54 and 56 at the righthand end. Between manifolds S0 and52, the wave engine is closed at the ends by extensions 42 and 44 of endplate 38, and between manifolds 54 and 56, by extensions 46 and 48 ofend plate 40.

The operation of the wave engine can best be understood with referenceto FIG. 6. The clockwise rotation of the rotor results in a motion ofthe tubes which in FIG. 6 is from top to bottom. The reactants arecontinuously introduced, for example at 1 atmosphere and 420 C., throughline 12 into manifold 50, from which they enter the left ends of thosetubes 36 which are in communication with the manifold 50. The reactantsfill those parts of the tubes on the left side of the interface 60,which is indicated in H0. 6 by a dashed line. On the left side of theinterface are reactants, and on the right side hydrogen.

The driving gas, hydrogen, is continuously introduced, e.g., at 12atmospheres and 420C. through line 14 into the manifold 52, from whichit is introduced into the left ends of the tubes which are incommunication with that manifold. The hydrogen fills those parts of thetubes on the left side of the interface 58, the reactants now being onthe right side of the interface 58. The reactants are subjected to ashock wave as a result of the sudden force of the high pressure drivinggas entering the tubes. This shock wave, traveling at a velocity ofabout Mach 5, moves along a path indicated by the line 62 in F IG. 6.The shock wave travels faster than the interface between the driving gasand the reactants, the velocity of the interface 58 and of the interface60 being about Mach l. The shock wave therefore passes ahead of theinterface 58 and travels through the reactant mixture. The latter isthereby shock-compressed to a pressure of about 8 atmospheres withresulting sudden rise in temperature to about l,200C. At thistemperature conversion of reactants to products takes place. Theproducts are expanded into manifold 56 and line 18, thereby rapidlycooling the reaction products and quenching the reaction. This rapidcooling provides a large increase in the yield of desired reactionproducts. The driving gas is withdrawn through manifold 54 and line 20.

The tubes are moving in a circular path, and therefore when a tubereaches the lower end of FIG. 6, it has returned to its originalposition, i.e., to the upper end of FIG. 6, and then begins a new cycleidentical with the one previously described.

After the driving gas has been expanded from the tubes into the drivinggas outlet manifold, the contents of the tubes are at a temperature ofthe same order of magnitude as that which prevailed prior to thecreation of the shock wave. A gas to act as a scavenging or coolingagent can be then introduced into the tubes if it is desired either tofurther cool the contents of the tube or to remove residual driving gasfrom the tube or both.

The scavenging or cooling gas can be any gas which is nonreactive at theprevailing conditions. it may be constituent or constituents of thereactant materials or reaction products, since such constituents aregenerally non-reactive at the conditions prevailing after removal of thedriving gas. Nitrogen is a preferred scavenging or cooling gas, butothers such as hydrogen, methane, etc., can be employed.

lf scavenging or cooling gas is used, such gas may be introduced intothe tubes through an inlet manifold,

- not shown in FIGS. 2 to 6, located below inlet manifold 52 as shown inFIG. 6. The additional inlet manifold would therefore be positioned sothat the left ends of the tubes come in communication with theadditional manifold after coming into communication with the manifold 52and before again coming into communication with manifold 50. A suitableoutlet manifold, also not shown, would also be provided, to come intocommunication with the right ends of the tubes after the tubes have comein communication with manifold 54 and before again coming intocommunication with manifold 56.

Turning to FIGS. 7 to 1], operation is therein illustrated whichinvolves the production of a reflected shock wave which results in thesubjection of the reactants to two shock waves in rapid succession. Eachshock wave produces a rapid heating of the reactants, and the use ofreflected shock wave makes it possible to obtain higher temperaturesthan those which are obtained with a single shock wave such as thatprovided in the operation previously described.

in the apparatus shown in FIGS. 7 to 11, the outlets for the driving gasand reaction products are on the same side of the tubes as the inletsfor the reactants and driving gas. The right ends of the tubes areclosed by end plate 40 and gases therefore cannot be removed from theright side of the tubes.

Referring to FIG. 11, reactants are continuously introduced, for exampleat 1 atmosphere and 420 C., through line 12 and manifold 50 into theleft ends of the tubes 36. At this time, the tubes contain a smallamount of reaction products from a previous cycle, and the introducedreactants commingle with these products. Subsequently, the left ends ofthe tubes come in communication with manifold 52 through which thedriving gas is introduced, for example at 12 atmospheres and 420C. Thedriving gas fills those parts of the tubes which are on the left side ofthe interface 64.

As a result of the introduction of the driving gas, a shock wave 68travels through the reactants to the far ends of the tubes, and thisshock wave compresses the reactants to a pressure of about 8atmospheres, thereby heating the gases to l,200C. On reaching the endplate 40, the shock wave is reflected toward the left ends of the tubesas a reflected shock wave 70, which further compresses the reactants andheats them to about 1,700C. The wave 70 pushes the interface betweenreactants and driving gas toward the left ends of the tubes as thereflected interface 66.

Driving gas is withdrawn through manifold 54 and line 20, and reactionproducts are evacuated through manifold 56 and line 18, leaving a smallamount of reaction products in the tubes for the next cycle, whichbegins with the introduction of fresh reactants through line 12 andmanifold 50.

If desired, a cooling gas can be introduced into the tubes following theevacuation of the reaction products and before the introduction of freshreactants. The principles involved in such introduction are generallysimilar to those described previously in connection with FIG. 6. Theinlet and outlet manifolds for such introduction and removal of coolinggas are preferably located on the same side of the tubes as the othermanifolds, though other arrangements can be used.

The use of a reflected shock wave, as illustrated in FIGS. 7 to 11, ispreferred because of the higher temperatures which are therebyobtainable while still maintaining a very short residence time.

A reflected shock wave is produced in another embodiment in operationwherein driving gas is introduced simultaneously from opposite ends of areaction tube containing reactant gas at lower pressure than the drivinggas. Two shock waves travel inwardly through the reactant gas to thecenter of the tube, where they meet and are reflected from each other,to travel outwardly through the reactant gas again. The driving gas isthen withdrawn from the tube; the reaction products are then withdrawnfrom the tube, which is then preferably scavenged prior to theintroduction of additional reactant gas and the beginning of anothercycle.

It is within the scope of the invention to provide any suitable numberof shock waves during a single cycle. In one embodiment, more than twoshocks can be provided. In this embodiment, instead of providing themanifold as an outlet for the driving gas, the reflected shock wave 70can be again reflected toward the right ends of the tubes as a thirdshock wave not shown, the driving gas and reactants being separatelywithdrawn from the right ends of the tubes through suitable means notshown. Alternatively, the shock wave can be reflected back again as afourth wave, etc. However, from the standpoint of simplicity of design Iand other features, it is preferred to provide only two shocks in acycle.

Two primary shocks may be applied to a reaction bqnixture by recyclingthe total effluent from the outlet o'hby passing the total effluent intoa second wave engine.

In its general aspect, the invention involves introducing reactant gasesand Hg vapors into a tube, introducing driving gas into the tubecontaining the reactants and Hg vapors, the latter introduction beingfrom either end of the tube or from both ends simultaneously, in eitherevent resulting in the subjection of the reactants to a shock wave, andthen separately removing driving gas and reaction products from the tubein any suitable order. The reactants, Hg diluent, and the driving gascan be introduced at the same or opposite ends of the tubes, and thereaction products and effluent driving gas can be removed at the same oropposite ends of the tube. In the light of the present specification, aperson skilled in the art can design a suitable apparatus for anydesired arrangement. From the standpoint of practicability, theapparatus illustrated in the drawing is preferred, but other apparatusis within the scope of the invention.

Hydrogen is much preferred for use as the driving gas according to theinvention, since its low density and high heat capacity ratio (k) makeit particularly suitable for this use. Gases having low density and highheat capacity ratio are very effective in creating a shock wave andthereby generating high pressure and temperature in the reactant gases.

Although hydrogen is the preferred driving gas, it is within the scopeof the invention to employ any other suitable gas, for example aconstituent or constituents of the reaction mixture, or some otherconstituent or constituents of the product mixture, or some inert gas,e.g., helium.

1n the process according to the invention, the reaction temperaturewhich is attained as a result of the shock wave or waves is preferablyin the range from 800 to 2,000C., and more preferably at least 1,200C.The residence time of reactants in the tubes is preferably in the rangefrom 0.0001 to 1.00 second, and more preferably in the range from 0.01to 0.1 second. With higher temperatures, it is generally desirable touse shorter residence times in order to avoid excessive decomposition ofreactants.

The pressure obtained in the reactant gases as a result of the shockwave or waves is preferably in the range from 5 to 30 atmospheres and isusually in the range from 5 to 15 atmospheres. The temperature andpressure obtained as a result of the shock wave or waves are inherenteffects of the initial temperature and pressure of the reactants anddriving gas, and also of the respective natures of the reactants, thevolume of Hg vapor and the driving gas, and are therefore subject toconsiderable variation.

The initial temperature of the driving gas as introduced into the tubesis preferably in the range from to 425C. The ratio of the initialdriving gas pressure to the initial reactant pressure is preferably inthe range from 5 to 50, and more preferably at least 10. Othertemperatures and pressures can be employed in some instances, and it iseven possible to employ a driving gas which is initially at roomtemperature and obtain significant heating as a result of the shockwave. However, in order to obtain a sufficiently high temperature for apractical process, it is generally necessary to preheat the driving gasand also the reactants.

In order to obtain a reaction temperature of 800C. or higher, it isgenerally necessary to use hydrogen as driving gas, a pressure ratio(i.e., initial ratio of driving gas pressure to reactant pressure) of atleast 5, an initial reactant temperature of at least 300C., and areflected shock wave. To obtain a reaction temperature of 1,500 C. orhigher, with hydrogen and a reflected shock wave, pressure ratio of atleast 20 and initial re actant temperatures of at least 400C. willusually be needed.

The residence times of gases in the tubes and the through-puts ofreactants and driving gas are functions of the design and operation ofthe apparatus. In the light of the present specification, a personskilled in the art can select proper design and operation in order toobtain desired residence times and through-puts for a given instance. Asan example, in an apparatus containing 35 tubes, each 6 inches long, andhaving crosssectional areas of 0.25 square inch, the apparatus beingrotated at 8,000 r.p.m. to provide a residence time of 0.002 second,through-puts of 0.1 to 0.2 pound of gas per second may typically beobtained.

Preferably, the driving gas, the reactants and the products are gasphase materials at the temperature of introduction into the reactiontubes. Where elemental carbon is employed as a reactant, it may beintroduced into the tubes as a suspension in nitrogenous gas. Gas phase,as the term is used herein, includes vapor phase.

The reaction according to the invention proceeds satisfactorily withouta catalyst. However, a known catalyst can be employed if desired, e.g.,as a coating on the insides of the tubes. The tubes themselves should befree of obstruction, in order that the shock wave may be satisfactorilypropagated.

The following examples will further illustrate the present invention.

EXAMPLES l-4 Cracking of Butane The conditions and results of four runsmade according to the procedure set out in describing the drawing areshown in Table ll.

TABLE 11 Run 1 2 3 4 Reactant Gas 1. butane vol I S l 2. Hg vol 0 90 960 3. Argon vol 0 0 0 99 4. Pressure psia 0.5 0.5 0.5 l0(psig) 5. Temp. C400 400 400 Driving Gas Hydrogen 1. Pressure psia 300 300 300 600(psig)2. Temp. C. 400 400 400 25 Products l. ethylene vol 2 44 49.8 2.acetylene vol k l 5 9 4.7 3. butane vol 65 47 7 0 based on totalhydrocarbons present in reactant gas The following examples were alsoconducted accord ing to the procedure set out in describing the drawing.The analysis were made by standard spectroscopic means.

EXAMPLE 5 Dissociation of Water Vapor The reactant gas mixturecontaining 1% H,0 by volume in 99% Hg is held at a temperature of 600Cand at a pressure of 75 psia in a wave engine. The driving gas,hydrogen, is introduced into a separate chamber until a pressure of 750psia is reached. The hydrogen is then released into the H O/Hg mixtureand shockcompresses the reactant gas mixture to about 20 atmosphereswith resulting temperature of about 3,300C.

Reaction equilibrium is reached at these conditions during the residencetime. The water vapor decomposes and a complete analysis of the productmixture by volume percent is:

H, o, 4 o 2 H 4 OH 1 H,O s

On expansion through an exit port or nozzle the hydrogen travels muchahead of the other gases and can, therefore, be separated. No oxides ofmercury are formed as they are considerably less stable than water.

EXAMPLE 6 Dissociation of Carbon Dioxide A charge gas of 1% CO, in 99%Hg by volume is introduced into the wave engine and pre-heated to 400Cat 2 atmospheres. Hydrogen at 20 atmospheres is released into the Co /Hgmixture and shock-compresses the charge gas to about 10 atmospheres withresulting temperatures of about 2,700C. The carbon dioxide de composesand upon separation and analysis of the product mixture by volumepercent yields:

CO, 67.5 C0 22.2 0 [0.3

EXAMPLE 7 Formation of Carbon Disulfide A reactant mixture containing 1%CH 1% H 8 in 98% Hg by volume was put into the wave engine andpre-heated to 400C. at 1 atmosphere. Hydrogen compressed to about 20atmospheres is introduced into the gas mixture and shock-wave producedcompresses the reactant mixture to about 8 atmospheres with a resultingtemperature of about 1,700C. The methane and hydrogen sulfide react toform carbon disulfide with acetylene and ethylene as by-products. Uponseparation a complete analysis of the product by volume percent is:

In all the above examples, the mercury vapor remains unchanged thereforehas not been included in the analysis.

The invention claimed is:

1. In a shock wave reaction for the dissociation of water wherein watervapor is subjected to one or more mechanical shock waves produced by adriving gas having an initial pressure in the range of 5 to 50atmospheres, the improvement which comprises adding mercury vapor as adiluent to the water vapor wherein the volume ratio of water vapor tomercury vapor is in the range of 1:2 to 1:200, and separating themercury from the product gas.

2. The process according to claim 1, wherein said water vapor andmercury vapor have an initial temperature on the order of 600C. and aninitial pressure on the order of 7S psia.

3. The process according to claim 1 in which the driving gas ishydrogen.

2. The process according to claim 1, wherein said water vapor and mercury vapor have an initial temperature on the order of 600* C. and an initial pressure on the order of 75 psia.
 3. The process according to claim 1 in which the driving gas is hydrogen. 